1. Field of the Invention
The present invention relates generally to a liquid crystal display device, and more particularly to a transflective liquid crystal display device which includes, within one pixel, a reflective part which displays an image by making use of ambient light, and a transmissive part which displays an image by making use of backlight.
2. Description of the Related Art
A transflective liquid crystal display device includes, within the same pixel, a reflective part having a reflective electrode, and a transmissive part having a transmissive electrode. The transflective liquid crystal display device functions as a transmissive liquid crystal display device which displays an image by selectively transmitting backlight by making use of the transmissive part within the pixel, and also functions as a reflective liquid crystal display device which displays an image by selectively reflecting ambient light by making use of the reflective part within the pixel. With this structure, the power consumption can greatly be reduced.
In a liquid crystal display device which is configured such that an insulation layer is interposed between a switch element and a pixel electrode, for example, a bottom-type thin-film transistor, which is the switch element, and the pixel electrode are electrically connected via a contact hole which is formed in a resin layer (see Jpn. Pat. Appln. KOKAI Publication No. 2003-43522).
In the transflective liquid crystal display device, a proper gap differs between the reflective part and the transmissive part. In many cases, the gap at the reflective part is set to be substantially half the gap at the transmissive part.
In the above-described structure in which the pixel electrode and the switch element are electrically connected via the contact hole that is formed at the reflective part, the gap at a region where the contact hole is formed is greater than the gap at the peripheral region. Consequently, in the region where the contact hole is formed, light leak occurs and the contrast ratio at the time of reflective display lowers.
In addition, in the transflective liquid crystal display device, the gap difference between the reflective part and the transmissive part is created by making use of the difference in film thickness of the insulation layer. In this case, it is possible that at the time of voltage application, an oblique electric field may be generated between the counter-electrode and the pixel electrode, at an end portion of the insulation layer. In particular, in the normally white mode, in the case of executing black display by generating an electric field between the pixel electrode and the counter-electrode, an alignment defect of liquid crystal molecules occurs due to an oblique electric field, and light leak occurs. This leads to a decrease in contrast ratio.